Output voltage regulation and maintaining the accuracy of the regulated voltage provided by a switch mode power converter can be a very demanding task. In the field of multi-function portable consumer electronic devices (also referred to here as mobile devices, such as smartphones, tablet computers, and laptop computers) the power requirements of the constituent components such as the display screen, the wireless communications interface, the audio subsystem, and the system on a chip (SoC) or applications processor are quite demanding. For example, in such devices, the load on an output node of a voltage regulator can exhibit sudden changes that are so great, e.g. as fast as 100 Amperes-1000 Amperes per microsecond, that the output node exhibits transient voltage droop. Attempts at reducing the transient voltage droop by the conventional approach of simply using larger load capacitance and higher performance decoupling and/or filter capacitors may not be practical in many instances.
Another solution to achieve fast transient recovery that has been suggested is a transient recovery circuit that responds only to fast changes in the load, so as to suppress both output voltage overshoot and undershoot (droop). The transient recovery circuit may operate independently of a regular feedback circuit that controls the phases of a multi-phase switching regulator more “slowly”, during steady state operation (when the load is not changing rapidly). The transient recovery circuit overrides a control voltage from the regular feedback circuit so as to control the duty cycle of a pulse width modulation circuit in the switching regulator, only during transient conditions. The transient recovery circuit may also control a dedicated phase, of a multi-phase switching regulator, and may remain inactive during non-transient conditions.